11 In vain, then, does the Apostle say: “I wrote to you, in an Epistle, not to mingle with fornicators;” and lest perchance they should say, We are not speaking of all the fornicators of the world, but we say that he who has been baptized in Christ ought not now to be esteemed a fornicator, but his life, whatever it is, is accepted of God, the Apostle has added “Not at all [meaning] with the fornicators of this world,” and farther on, “If any that is named a brother be a fornicator, or covetous, or an idolator, or a reviler, or a drunkard, or an extortioner, with such an one not even to eat.
For what have I to do with judging them that are without?” And to the Ephesians: “But fornication, and all uncleanness, and covetousness let it not even be named among you, as becomes saints.” And immediately he adds: “For this you know, that no immodest person, nor unclean, nor covetous, which is an idolator, has any inheritance in the kingdom of Christ and of God.” It is clear that this is said of the baptized, for they receive the inheritance, who are baptized into the death of Christ and are buried together with Him, that they may rise again with Him.
Therefore they are heirs of God, and joint heirs with Christ: heirs of God, because the grace of Christ is conveyed to them; joint-heirs with Christ, because they are renewed into His life; heirs also of Christ; because to them is given by His death as it were the inheritance of the testator.
Source: Letters (New Advent)